The present invention relates to dry ice producing machines used in supermarkets or other places for keeping fresh foods or other takeout items cool.
In such cases, conventionally, salesclerks crush a large volume of dry ice into small pieces and add the crushed pieces to the bag or box of takeout items. Since a direct touch to dry ice causes frostbite or may be harmful in other ways, careful treatment is necessary in handling dry ice: by wearing gloves in crushing dry ice, for example. This prevents quick response to the customers"" request and requires additional workforce in retail shops selling fresh food or other goods which need cooling after sales.
In view of the above problems, the present applicant has proposed in the Japanese Patent Application No. H09-362597 (Publication No. H11-171525) a dry ice producing machine including: an operating chamber, a horn provided in an upper part of the operating chamber, a nozzle provided at a top of the horn for ejecting carbon dioxide. The machine enables rapid and safe delivery of powdered dry ice around items in a retail shop, etc.
In the above dry ice producing machine, the ejecting time of the carbon dioxide was made constant. A problem with the dry ice producing machine was that the amount of dry ice produced was not constant due to various conditions. The present invention is achieved in view of the new problem.
The first dry ice producing machine according to the present invention includes: a supplying chamber; a horn provided in an upper part of the supplying chamber; a nozzle for ejecting carbon dioxide provided at a top of the horn; a sensor for measuring an ambient temperature; and a controller for determining the length of time for ejecting the carbon dioxide to produce a preset amount of dry ice according to the ambient temperature.
When the dry ice producing machine is placed in a high temperature atmosphere, a longer carbon dioxide ejecting time is needed to produce the same amount of dry ice. Accordingly, the controller determines the length of ejecting time according to the ambient temperature. The time length may be determined using a mathematical function or alternatively using a look-up table or tables prepared beforehand through experiments or through experiments and calculations. The amount of dry ice to be produced may be fixed or preset by the operator or user.
The second dry ice producing machine according to the present invention includes: a supplying chamber; a horn provided in an upper part of the supplying chamber; a nozzle for ejecting carbon dioxide provided at the top of the horn; a sensor for measuring the pressure of the carbon dioxide; and a controller for determining the length of time for ejecting the carbon dioxide to produce a preset amount of dry ice according to the pressure.
When the carbon dioxide is supplied from a bomb or a tank, and the pressure of the carbon dioxide in the bomb/tank is low, a longer ejecting time is needed to produce the same amount of dry ice. It is also the case when the carbon dioxide is supplied through a pipe line from the production site, or from other sources. The pressure is also, besides the ambient temperature, a parameter for changing the amount of dry ice produced. Accordingly, the controller determines the length of ejecting time according to the pressure. As described above, the time length may be determined using a mathematical function or alternatively using a look-up table or tables. The amount of dry ice to be produced may be fixed or preset by the operator or user.
The third dry ice producing machine according to the present invention includes: a supplying chamber; a horn provided in the upper part of the supplying chamber; a nozzle for ejecting carbon dioxide provided at the top of the horn; a timer for measuring an interval time since the last ejection of the carbon dioxide; and a controller for determining the length of time for ejecting the carbon dioxide to produce a preset amount of dry ice according to the interval time.
Just after an amount of carbon dioxide is ejected and the dry ice is produced, the horn or pipe is still cool. But the temperature gradually rises to the ambient temperature as time passes. While the temperature of the horn or pipe is still low, a larger amount of dry ice is produced, but the producing amount gradually decreases as time passes and the temperature of the horn or pipe rises. Thus, similarly to the former two cases, the controller determines the length of ejecting time according to the interval time since the last ejection. Also the time length may be determined using a mathematical function or alternatively using a look-up table or tables, and the amount of dry ice to be produced may be fixed or preset by the operator or user.
As described above, the dry ice producing machine according to the present invention can always produce a preset amount of dry ice regardless of various disturbing parameters such as ambient temperature, gas pressure or ejecting interval time. With the advantages of convenience and safety, the machine of the present invention is suited for use as an automatic supplying machine placed in supermarkets or retail shops. In this case, a money (coin/bill) operator may be installed in the machine.
In the above description of the present invention, the three parameters, i.e., ambient temperature, gas pressure and interval time, are independently used in a dry ice producing machine. It is of course possible to use two or three of these parameters together. When, for example, the highest precision of control is sought, all of the ambient temperature sensor 2, the gas pressure sensor 3 and the interval timer 4 (FIG. 1) are used to determine the ejecting time length in the ejecting time determiner 1. In the case of FIG. 1, data of the determined ejecting time length is sent to the valve controller 6, which opens the valve of the nozzle 7 for the ejecting time length. This produces a preset amount of dry ice. When the nozzle valve 7 is closed and ejection is terminated, data of the terminating time point is sent from the valve controller 6 to the time memory 5, where the data is stored. The interval timer 4 reads out the data, and calculates the interval time by subtracting the data from the data of the current time.
When, on the other hand, the dry ice producing machine is used in such a place where the ambient temperature hardly changes, the gas pressure and the interval time are sufficient to determine the ejecting time length. When carbon dioxide of a constant pressure is supplied, the gas pressure sensor 3 is unnecessary. When the volume of the gas bomb/tank is large enough so that the gas pressure can be regarded constant, the gas pressure sensor 3 is unnecessary either, or it is replaced by a manual pressure selection switch. In this case, the operator or user selects the position of the switch from time to time regarding the time of usage or judging from the amount of dry ice actually produced.